Knowledge of antimicrobial use in hospitals is quite substantial, while in nursing homes the use of these drugs has been inadequately studied. Not only is there inadequate information on such basic features as the incidence and type of antimicrobial use per patient but also of a number of other matters relevant to optimal medical care. For instance the proportion of patients who are prescribed antimicrobials in the absence of a physical examination, microbiologic evaluation and establishment of a diagnosis of suspected or known bacterial infection is unknown. The proposed study addresses two major hypotheses: 1. That a large proportion of antimicrobials are prescribed to patients without documented physical or microbiologic examination, without a stated or implied diagnosis of bacterial infection, and without documented monitoring of either effectiveness or adverse reactions; 2. That the incidence and type of antimicrobial use is associated with: prescribing physician characteristics such as age, date of medical graduation and specialty; patient characteristics such as level of care, age and sex; and nursing home characteristics such as bed size, geographic location and type of ownership. A random sample of nursing homes in the State of Maryland will be chosen, stratified according to type of care (chronic, comprehensive, domiciliary) and bed size. Approximately 50 facilities will be necessary to obtain the desired sample of 3400 patients. A cohort consisting of all patients in the homes as of a specific date, who are 65 or older, will be identified. The medical records of all of these patients will be reviewed for two six-month periods for the presence of an antimicrobial order. Whenever an antimicrobial is prescribed, data will be collected concerning physical examination, bacterial cultures and monitoring. We will compare the incidence or proportions of antimicrobial use to those factors outlined in the above hypotheses. This study will represent a systematic evaluation of how physicians prescribe antimicrobials for nursing home patients. The eventual goal of this and subsequent studies is to develop guidelines for the evaluation of possibly infected patients and for antimicrobial use.